# $WW\to t\bar{t}$ growth

I was told recently that "it is well known that processes like $WW\to t\bar{t}$ ($t$ being a top, or any massive fermion) grows linearly with the energy in the absence of an Higgs boson." Does anyone know of a reference? The only ones I can find regarding the growth of $WW \to f\bar{f}$ are about the old argument for having a neutral current, i.e. $WW \to f\bar{f}$ cross-section grows if $Z$-mediated diagrams are not included.